The Amiga chipset used DMA very extensively, so the CPU's memory access speed is not as important as on other machines. There were other architectural constraints, like the fact that the CPU had to compete with such chips for access to the same memory. So-called Fast memory was not a default setup for years. And the true solution, dual-ported RAM would have been too expensive.

Which games do you think were constrained by the CPU? I can think of other factors first:

- sloppy ports

- it was a more complex system to tame than most of those that preceded it

- the sprites were simply too limited, so you had to use the Blitter a lot

- unlike a lot of chips of the era, Denise had no tile or character generator so, again, you had to use the Blitter

- the CPU was clocked at 7.14MHz to align with the PAL/NTSC clock even if it could run at 8MHz

- if you used more than four bitplanes in low resolution, the Agnus chip would let Denise starve the CPU even on cycles where the latter would normally have access (if you set the right bit, the Blitter could be allowed to win, too)

I don't see how a different CPU would have helped with any of the above. In a time period during which memory wasn't typically the limit, the Amiga was one of the first systems where the CPU starved for it.

The X68000 was better, sure, but it came out later and, being in the same mold as the arcade systems of the era, it had dedicated video RAM, tiles and more powerful, actually useful sprites.

I think you remember wrong. Most of the games were ports from the Atari ST and seldom used the blitter, sprites or dual-playfield. When you have a 80's computer with pretty severe limitations you often design your game visuals around those limitations.

As for your statement on "many of the 8-bit machines", only the C64 had good 50/60fps shooters of the 8-bit home computers. The 8-bit consoles had better graphics hardware than the C64 and sometimes had the better games.

Properly implemented Amiga games were not that many though. It was hard to utilize the machine and it required good graphic artists to make it look fresh and sharp with the limitations of dual playfields.

But take a look at these games, I think they all run on a 512kb chipmem only OCS Amiga.

Mega Typhoon: https://www.youtube.com/watch?v=zk3LNdPTnMw

Agony: https://www.youtube.com/watch?v=a839o59Bt4s

Apidya: https://www.youtube.com/watch?v=QBJNbDidxcM

And of course the R-Type and Turrican series. Those were 12 or 25fps on the ST but silky smooth 50fps on the Amiga 500. Especially Mega Typhoon looks like a Raiden clone. It's very hectic, lots of bullets and big enemies and snake formations. The only thing that stands out is the lack of colors. I suspect this is because of using dual playfield and that limits the number of colors to 8+8+sprite colors.

I'm an old demo coder(C64 and Amiga) and was very picky about framerate back then. The only shootemups I liked that was not 50fps was Battle Squadron and Wings of Death.

And then you talk vaguely about responsiveness. Do you mean the number of cycles spent by the machinery to process and IRQ? I never saw that as a problem. On the Atari ST they use timer IRQ's to make rasterbars in demos and games. Seems to me they would not do that if the cost was too high.

The Amiga mouse-pointer was a sprite. I never saw a delay on that. It felt like a game character. At most 1 frame delay. And dragging Amiga "screens" up and down was usually only one frame after the sprite movement. But that's logical since the system copperlist has to be updated and that is definitely one frame delay on that.

Frame rate? I don't see how any lack of framerate on Amiga was due to CPU because peripheral chips performed all the video and audio using DMA from dedicated graphics (CHIP) memory.

Again, what "responsiveness"? There doesn't seem to be any problem with that on Amiga other than what you say.